Brew Your Own Compost Tea

What is compost tea? What does it do? 

Compost tea is a liquid compost extract. There are several varieties of compost tea – the type used at Lotusland is actively aerated compost tea (AACT). To put it simply, a bag of compost is soaked in aerated water for approximately 24 hours, leaching nutrients and beneficial microorganisms into a solution called compost tea. 

When applied to soil and plant foliage, this solution increases microorganism populations and diversity. In the soil, the microorganisms contained in compost tea convert the nutrients contained in organic fertilizers, soil organic matter, and minerals into plant-available forms at the right time (during active plant growth) and location (at the root tips) to be of the most benefit to plants. When applied to foliage, plants absorb compost tea’s nutrients through their leaves, while the microorganisms contained in the solution create a biofilm which helps to suppress foliar diseases. Drenching applications are especially helpful where soil has been degraded by prior activities, such as compaction or the use of synthetic fertilizers. Compost tea is one of the fastest ways to reintroduce the organisms necessary for a healthy soil biology.   

Gather supplies and build your brewer 

Compost tea brewers are available online in a range of sizes. For most home gardeners, an adequately-sized brewer can be made in a 5-gallon bucket.  

Besides the bucket and high-quality compost, all you will need is a sturdy mesh bag to contain the compost (even a sock will do), a food source for the microorganisms (molasses, kelp, humic acids, meal-based fertilizers, etc…), and a pump to aerate the water during the brewing process (this keeps it from going anaerobic and breeding pathogenic organisms). A pump used for a fish tank (an airstone) will work for a 5-gallon set-up, larger brewers will require a larger pump. Aim for 9 ppm oxygen or more. If you’re unsure whether your tea is adequately aerated, purchase a dissolved oxygen meter to be sure. 

When it comes time to apply your tea, you will most likely want a sprayer of some kind. A backpack sprayer or a handheld pump sprayer will work well for the average home. For small applications, a spray bottle will work. For covering large areas, a trailer sprayer is helpful.  Compost tea does not require spray application – it can be used as a drench that is poured directly onto soil. 

Source your compost and water 

High quality compost tea begins with high quality compost. Compost tea will contain many of the species of organisms that are present in the compost used to brew it – the more beneficial organisms in the compost, the better the final product.  

Lotusland maintains a compost pile specifically dedicated to compost tea brewing. This pile is made up only of oak chips and oak leaves – with a dusting of organic fertilizers to encourage populations of bacteria, fungi, and earthworms.  Building a pile composed solely of native tree material ensures that the final product will be full of fungi and other indigenous microorganisms. 

Composting native plant material from your property is the best option, but not available to everyone. You can still create high-quality compost from other yard waste or from your kitchen scraps. Worm castings created by vermicomposting will work as well.  

You’ll also need a source of non-chlorinated water. (Chlorine and chloramines will kill the beneficial microorganisms that are the goal of compost tea.) You can use well water, rain water, or reverse osmosis water. Alternatively, if chlorinated tap water is left to sit in the open for 24-36 hours, the chlorine will have dissipated, though some chloramines might remain depending on your tap water. These chloramines can be neutralized by adding humic acids, among other products. 

Get Brewing 

Fill your mesh bag with compost and your bucket with non-chlorinated water. Place the aerator and the compost-filled bag in the water-filled bucket. Add your food source. Start the pump and aerate for at least 24-hours. A brown froth of bubbles should form at the top of the bucket – this is evidence that the microorganisms you’re seeking are alive and active. 

After brewing for 24 hours, the tea is ready to be used. If you’re planning to apply your tea with a sprayer, it can be helpful to strain it through a sieve to remove larger particles that might cause a clog. If you’re pouring tea directly onto the soil, then this step isn’t necessary. 

Be sure to promptly and thoroughly rinse out your tea brewer after brewing is complete in order to prevent the growth of pathogenic organisms. 

Apply your tea 

Tea can be applied via sprayer to foliage and the soil. It can also be poured directly onto the soil or injected into the ground (this requires a special tool). The resulting boost in microorganism biodiversity leads to improved soil fertility and structure, and ultimately to healthier plants that stand up better to stressors such as drought and disease. 

Tea can safely be applied undiluted to plantings. However, at Lotusland, tea is typically diluted in order to cover more area. If you’d like, you can add additional water-soluble fertilizers and amendments to increase the range and quantity of the tea’s nutrients. Lotusland has used kelp and fish, among other products. With these additions, compost tea becomes a biology-packed carrier for organic, water-soluble fertilizers.    

It is important that tea be applied shortly after brewing, while the microbes are still active and alive. Soon after active aeration has ended, anaerobic conditions slowly begin to develop.  This is not a problem for the first few hours, but over a longer period, it will result in the die-off of beneficial aerobic organisms and the growth of unwanted anaerobic organisms. It is due to this short shelf-life that Lotusland does not sell compost tea and that it cannot be bought.